JP7299196B2 - fuel cell system - Google Patents

Description

The present disclosure relates to fuel cell systems.

Japanese Patent Laid-Open No. 2004-100000 discloses that the valve opening degree is controlled with high accuracy by learning to fully close the electronic throttle so that the idling speed is stabilized during idling after the engine is started.

Japanese Unexamined Patent Publication No. 2008-88925

In the fuel cell system, the valves provided in the air supply system and the hydrogen gas supply system are required to have a sealing property while the operation is stopped. Therefore, a seal member such as rubber is provided between the valve element and the body (bore). is common. In this case, when the valve is in a fully closed state, the valve body is brought into close contact with the sealing member to seal the flow path.

Here, the pressure (straining force) generated between the valve body and the sealing member may vary depending on the environment and manufacturing variations. Therefore, when the conventional valve opening control method described in Patent Document 1 and the like is applied to the control of the valves of the fuel cell system, feedback control of the valve opening at the time of system start-up due to the above-mentioned variation in the strain force. becomes unstable and an overshoot exceeding the target value may occur.

An object of the present disclosure is to provide a fuel cell system capable of stably controlling valve opening.

A fuel cell system according to an aspect of an embodiment of the present invention includes a valve arranged in a flow path through which a reactant gas supplied to a fuel cell flows, and a valve opening degree determination unit that determines the degree of opening of the valve based on the flow rate; a valve opening degree measurement unit that measures the degree of opening of the valve; a valve control unit that feedback-controls operation of the valve, wherein the valve control unit satisfies a first condition that the valve opening command value determined by the valve opening determination unit is less than a command value threshold, and When the valve opening measurement value measured by the valve opening measurement unit satisfies the second condition that the valve opening measurement value is less than the measurement value threshold value, the feedback control of the valve is not performed, and the first condition or the second condition is satisfied. is not satisfied, the feedback control of the valve is performed.

According to the present disclosure, it is possible to provide a fuel cell system capable of stably controlling the valve opening degree.

1 is a diagram showing a schematic configuration of a fuel cell system according to an embodiment; FIG. Functional block diagram of the control device in FIG. Schematic diagram showing the schematic configuration of the discharge flow rate adjustment valve Flowchart of valve control at startup of the fuel cell system Timing chart at startup of fuel cell system Timing chart when restarting the fuel cell system

Embodiments will be described below with reference to the accompanying drawings. In order to facilitate understanding of the description, the same constituent elements in each drawing are denoted by the same reference numerals as much as possible, and overlapping descriptions are omitted.

FIG. 1 is a diagram showing a schematic configuration of a fuel cell system 10 according to an embodiment. The fuel cell system 10 is mounted in a vehicle (fuel cell vehicle), for example, and outputs electric power as a power source of the vehicle in response to a driver's request. The fuel cell system 10 includes a fuel cell (FC) 100 , an air supply system 200 , a hydrogen gas supply system 300 , a cooling system (not shown), and a control device 600 .

The fuel cell 100 has a stack structure in which a plurality of unit cells 110 as power generating bodies are stacked. The single cell 110 includes a membrane electrode assembly (MEA) in which both electrodes of an anode and a cathode are joined to both sides of an electrolyte membrane, and two separators sandwiched from both sides of the anode and cathode of the membrane electrode assembly. It is composed of The fuel cell 100 is an electrochemical reaction of hydrogen as a fuel gas supplied to the anode from a hydrogen gas supply system 300, which will be described later, and oxygen as an oxidizing gas contained in air supplied to the cathode from an air supply system 200. Electricity is generated by the reaction, and the generated electric power drives a load such as a drive motor.

The air supply system 200 supplies air containing oxygen, which is an oxidizing gas, to the cathode of the fuel cell 100 . The air supply system 200 includes an oxygen supply channel 210 , a discharge channel 220 , a compressor 230 and a discharge flow control valve 240 . One end of the oxygen supply channel 210 is connected to the inlet of the cathode of the fuel cell 100, and the other end is an open end. Compressor 230 is provided in oxygen supply channel 210 . One end of the discharge channel 220 is connected to the outlet of the cathode of the fuel cell. A discharge flow control valve 240 is provided in the discharge channel 220 . The air supply system 200 supplies the air taken in from the open end of the oxygen supply channel 210 to the cathode of the fuel cell 100 after the compressor 230 adjusts the flow rate of the air. In addition, the air supply system 200 discharges air containing unconsumed oxygen (cathode off-gas) discharged from the outlet of the cathode into the atmosphere at a flow rate adjusted by the discharge flow control valve 240 of the discharge channel 220 . The operation of the air supply system 200 is performed by controlling the compressor 230 and the discharge flow control valve 240 by the controller 600, which will be described later. In the following description of the present embodiment, the discharge flow rate adjustment valve is used as a control target of the valve control described later with reference to FIG. The valve 240 will be described as an example. Also, the discharge flow control valve 240 may be described as "FC outlet air valve", "air outlet valve", "air valve", or the like.

The hydrogen gas supply system 300 supplies the anode of the fuel cell 100 with hydrogen, which is the fuel gas used for power generation of the fuel cell 100 . The hydrogen gas supply system 300 includes a hydrogen gas tank 310 as a fuel tank, a hydrogen gas supply path 320 as a fuel gas supply path, a reflux path 330, an opening/closing valve 340, a pressure regulating valve 350, and a fuel gas supply device. pressure sensors 321 and 322 , a relief valve 323 , a hydrogen gas pump 370 , a gas-liquid separator 380 , a discharge valve 395 and a discharge channel 390 . Note that the discharge channel 390 is connected to the discharge channel 220 .

The hydrogen gas tank 310 stores high pressure hydrogen gas. The hydrogen gas tank 310 is connected to the anode inlet of the fuel cell 100 via a hydrogen gas supply line 320 . The hydrogen gas supply path 320 is provided with an on-off valve 340, a pressure regulating valve 350, a pressure sensor 321, an injector 360, a relief valve 323, and a pressure sensor 322 in this order from the hydrogen gas tank 310 side. . The open/close valve 340 turns on/off the supply of the anode gas from the hydrogen gas tank 310 . Pressure regulating valve 350 regulates the pressure of hydrogen gas supplied to injector 360 . The injector 360 injects the hydrogen gas supplied from the pressure regulating valve 350 toward the anode of the fuel cell 100 through the hydrogen gas supply path 320 at intervals corresponding to the required load. Adjust the supply of hydrogen gas. The pressure on the upstream side of injector 360 is detected by pressure sensor 321 and the pressure on the downstream side of injector 360 is detected by pressure sensor 322 . The relief valve 323 operates (opens) when a preset pressure is exceeded, and releases the hydrogen gas flowing through the hydrogen gas supply passage 320 on the downstream side of the injector 360 from the release port of the relief valve 323 . As a result, the relief valve 323 operates so that the pressure in the hydrogen gas supply line 320 on the downstream side of the injector 360 does not exceed the set pressure. A heat flow sensor 324 is provided at the end of the discharge pipe 325 connected to the discharge port of the relief valve 323 , that is, directly downstream of the relief valve 323 . As will be described later, the heat flux sensor 324 detects changes in heat flux caused by the start of hydrogen gas release from the release port when the relief valve 323 is opened.

The hydrogen gas supplied to the fuel cell 100 through the hydrogen gas supply channel 320 flows through a supply-side hydrogen gas flow channel (not shown) configured by stacking a plurality of unit cells 110, and flows through each unit cell 110. supplied to Anode off-gas containing unused hydrogen gas that has not been used in each unit cell flows through a discharge-side hydrogen gas flow passage formed by stacking a plurality of unit cells 110 and is discharged to a reflux passage 330. This anode off-gas contains liquid water generated by power generation in each unit cell 110 and impurity gas such as nitrogen gas permeated from the cathode side to the anode side. That is, the anode off-gas is a mixed gas containing hydrogen gas and impurity gas such as nitrogen gas.

The return path 330 is connected to the outlet of the anode of the fuel cell 100 and the portion of the hydrogen gas supply path 320 closer to the fuel cell 100 than the pressure sensor 322, and the anode off-gas discharged from the fuel cell 100 is supplied to the hydrogen gas. Return to path 320 . The reflux path 330 is provided with a gas-liquid separator 380 and a hydrogen gas pump 370 . The gas-liquid separator 380 separates liquid water from the liquid-water-mixed anode off-gas discharged from the fuel cell 100 . The anode off-gas from which liquid water has been separated by the gas-liquid separator 380 is returned to the hydrogen gas supply path 320 via the reflux path 330 by the hydrogen gas pump 370, and the hydrogen gas contained in the anode off-gas is circulated and supplied to the fuel cell 100. be done. Therefore, the anode gas (fuel gas) supplied to the fuel cell 100 is actually a mixed gas containing hydrogen gas and impurity gas.

For efficient power generation by the fuel cell 100, it is not preferable that the impurity gas concentration is high and the hydrogen gas concentration is low. Therefore, when the concentration of the non-conformant gas contained in the anode off-gas is high and the concentration of hydrogen gas is low, the discharge valve 395 is opened to discharge the anode off-gas from the gas-liquid separator 380 to the discharge channel 390. control is performed. At this time, by injecting hydrogen gas from the injector 360, the concentration of the impurity gas is lowered and the concentration of the hydrogen gas is increased.

Various operations of the hydrogen gas supply system 300 are performed by controlling the opening/closing valve 340, the pressure regulating valve 350, the injector 360, the hydrogen gas pump 370, and the discharge valve 395 by the controller 600, which will be described later.

The control device 600 is composed of a so-called microcomputer having a CPU, ROM, RAM, etc. for executing logical operations. The control device 600 receives sensor inputs from pressure sensors 321 and 322, a heat flow sensor 324, an air valve opening sensor 63 (see FIG. 2), which will be described later, and various sensors (not shown), and controls the compressor 230, the injector 360, and the pressure regulator. Various controls are performed on each component in the fuel cell 100 such as the valve 350, the opening/closing valve 340, the discharge valve 395, the discharge flow control valve 240, and the like.

The control device 600 also controls the operation of the fuel cell 100 by controlling the air supply system 200, the hydrogen gas supply system 300, and the like. Further, based on the amount of change in the detection results of the pressure sensors 321 and 322, gas leaks, malfunctions including the actuation (valve opening) of the relief valve 323, malfunctions of various valves, and the like are detected.

In addition, the control device 600 can control the opening degrees of various valves such as the discharge flow control valve 240 using a feedback control method such as PID control. Control parameters for PID control can be acquired in advance through, for example, prior simulations, experiments, or the like. In particular, in the present embodiment, in the control of the discharge flow rate adjustment valve 240, it is possible to determine whether or not PID control can be performed according to a predetermined condition, which will be described later, and switch.

FIG. 2 is a functional block diagram of control device 600 in FIG. An air valve opening sensor 63 (valve opening measuring section) and the discharge flow rate adjusting valve 240 are connected to the control device 600 . The air valve opening sensor 63 measures the opening (valve opening measurement value) θm of the discharge flow control valve 240 provided in the air supply system 200 .

The control device 600 controls the operation of each element of the system, such as the discharge flow control valve 240, based on various types of system information input from the air valve opening sensor 63 and the like.

The control device 600 particularly includes a valve opening determination section 61 and an air valve control section 62 as shown in FIG.

The valve opening degree determination unit 61 calculates a command value θd for the opening degree of the discharge flow rate adjustment valve 240 . The valve opening command value θd is determined, for example, based on the flow rate of the reaction gas calculated from the target power generation amount of the fuel cell 100 .

The air valve control section 62 controls the operation of the discharge flow rate adjustment valve 240 based on the air valve opening command value θd calculated by the valve opening determination section 61 . The air valve control unit 62 performs feedback control such as PID control so that the valve opening of the exhaust flow control valve 240 (measured air valve opening θm measured by the air valve opening sensor 63) follows the command value θd. conduct.

Further, the air valve control unit 62 determines whether PID control can be performed based on the air valve opening measurement value θm measured by the air valve opening sensor 63 and the air valve opening command value θd calculated by the valve opening determination unit 61. decide.

Here, with reference to FIG. 3, a schematic configuration of the valves provided in the fuel cell system 10 and conventional problems will be described. FIG. 3 is a schematic diagram showing a schematic configuration of a discharge flow control valve 240 as an example of a valve provided in the fuel cell system 10. As shown in FIG.

As shown in FIG. 3, the exhaust flow control valve 240 has a disk-shaped disc (valve element) 242 that is rotated at approximately 90 degrees with a stem (valve stem) 246 as an axis in a flow path (bore) inside a valve body 241, for example. It is a so-called butterfly valve, which is configured to open and close by rotating. The exhaust flow control valve 240 rotates around the valve stem 246 by the driving force f1 output by the motor 243 . A biasing means such as a spring 244 is connected to the valve stem 246, and a biasing force f2 is applied in the direction in which the valve body 242 is fully closed. In other words, the discharge flow control valve 240 is a valve that maintains a fully closed state by the biasing force f2 of the spring 244 when the energization to the valve is cut off and the driving force f1 by the motor 243 is not applied. is. When opening the valve, the motor 243 outputs a torque opposite to the biasing force f2 in the closing direction, thereby realizing the valve opening operation.

In addition, the FC outlet air valve (exhaust flow rate adjustment valve 240) provided in the discharge passage 220 of the air supply system 200 of the fuel cell system 10 has an upper limit to the concentration of hydrogen contained in the exhaust gas. Sealability is required during stop (fully closed state). Therefore, as shown in FIG. 3, a rubber lip 245 is provided between the valve body 242 and the bore of the valve body 241 so that the valve body 242 is in close contact with the rubber lip 245 when the valve is fully closed. It is configured so as to improve the sealing performance.

Here, as described above, when the control of the valve opening degree of the exhaust flow rate adjustment valve 240 is performed by feedback control such as PID control, the control parameters used for PID control are obtained in advance by, for example, simulations or experiments in advance. I often use something else. However, the pressure (straining force) generated between the valve body 242 and the rubber lip 245 may vary due to differences in usage environments of individual valves, manufacturing variations, and the like. For this reason, if the pressure between the valve body 242 and the rubber lip 245 differs from that at the time of parameter acquisition due to this variation in straining force, a low opening state close to a fully closed state, such as an idling state at system start-up, may occur. At this time, the feedback control of the valve opening becomes unstable and this opening cannot be maintained, and overshoot may occur in which the valve opening increases significantly beyond the target value.

Therefore, in the present embodiment, the air valve control unit 62 of the control device 600 satisfies the condition (first condition) that the valve opening command value θd is less than the command value threshold θt1, including the state immediately after the system is started, PID control is not performed (energization is cut), thereby suppressing the occurrence of valve opening overshoot when the system is started.

However, if the first condition is the only condition for stopping the execution of PID control, there is a possibility that problems may occur in situations other than when the system is started. In other words, if the valve body 242 of the valve that is being stopped is accelerated in the closing direction and is restarted, the energization to the valve is cut off in order to satisfy the first condition. In some cases, the braking force of 243 is lost and the valve body 242 is closed at a speed exceeding the durability of the parts.

Therefore, in the present embodiment, in addition to the above-described first condition, the air valve control unit 62 of the control device 600 has a condition that the actual valve opening (valve opening measured value θm) is less than the measured value threshold θt2 (second condition ) is also satisfied, PID control is not performed (energization is cut). In other words, even when the valve opening command value θd is less than the command value threshold θt1, such as when the system is restarted, PID control is performed when the actual valve opening is greater than the threshold θt2. This prevents the valve body 242 from colliding with the valve main body 241 at high speed when the system is restarted, thereby protecting the parts.

That is, in the present embodiment, the air valve control unit 62 of the control device 600 does not perform PID control of the valve opening only when both the first condition and the second condition are satisfied. PID control is performed when at least one of the conditions is not satisfied. As a result, the fuel cell system 10 of the present embodiment can suppress the occurrence of overshoot at system start-up, and can also prevent collision of the valve body 242 at system restart. It can be carried out.

The effects of this embodiment will be further described with reference to FIGS. 4 to 6. FIG. FIG. 4 is a flow chart of valve control when the fuel cell system 10 is started. Each process in the flowchart of FIG. 4 is performed by the control device 600 .

In step S1, an instruction to prepare for power generation of the FC stack (fuel cell 100) is issued, and in step S2, energization of the air outlet valve (exhaust flow control valve 240) is permitted.

In step S3, the air valve control unit 62 determines whether or not the following two conditions for determining whether PID control of the valve opening degree of the discharge flow control valve 240 can be performed are satisfied.
First condition: the valve opening command value θd is less than the command value threshold θt1.
Second condition: the valve opening measurement value θm is less than the measurement value threshold value θt2.

Here, the valve opening degree command value θd is calculated by the valve opening degree determination unit 61 according to the power generation amount of the fuel cell 100, for example. The valve opening measurement value θm is measured by the air valve opening sensor 63 . The command value threshold θt1 and the measured value threshold θt2 can be set individually. The command value threshold θt1 is, for example, 3 (deg), and the measured value threshold θt2 is, for example, 2.5 (deg).

As a result of the determination in step S3, when both the first condition and the second condition are satisfied (Yes in step S3), the process proceeds to step S4, and PID control is not performed during the period when this condition is satisfied.

On the other hand, if at least one of the first condition and the second condition is not satisfied (No in step S3), the process proceeds to step S5, PID control calculation for valve drive is started, and PID control is performed.

After execution of the processes of steps S4 and S5, the process returns to the determination block of step S3, and determination of whether or not PID control can be performed is repeated.

FIG. 5 is a timing chart when the fuel cell system 10 is started. FIG. 5 shows the ignition (IG), the drive permission signal of the air valve (exhaust flow rate adjustment valve 240), the valve opening command value θd, the valve opening measurement value θm, the rotation speed of the air compressor (ACP), and the time of the PID permission signal. Transitions are shown. In the valve opening measurement value θm, the solid line indicates the behavior when the present embodiment is applied, and the dotted line indicates the conventional behavior (when PID control is started immediately after driving is permitted). Similarly, the PID enable signal is also indicated by a solid line in the present embodiment and by a dotted line in the conventional case.

When the ignition is switched to ON at time T1, the processing of steps S1 and S2 in the flowchart of FIG. 4 is executed, and the drive permission signal rises at time T2.

At this time, the valve opening command value θd becomes a low opening θ1 (for example, 0.5 degrees) close to the fully closed state. Conventionally, the PID permission signal rises at the same time as the drive permission signal rises, and feedback control of the valve opening is started. Due to individual differences, feedback control at low opening cannot be performed well. Overshoot may occur.

On the other hand, in the present embodiment, the processing of steps S3 to S4 in the flowchart of FIG. does not implement PID control. Therefore, it is possible to suppress the occurrence of overshoot of the air valve 240 immediately after startup.

At time T3, when a power generation command is issued and air supply to the stack of the fuel cell 100 is started, the valve opening command value θd increases until it exceeds the command value threshold value θt1. At this time, since the first condition is no longer satisfied, the processing of steps S3 to S5 in the flowchart of FIG. increases so as to follow the valve opening command value θd.

As described above, according to the present embodiment, it is possible to suppress the occurrence of overshoot of the air valve 240 when the fuel cell system 10 is started.

FIG. 6 is a timing chart when the fuel cell system 10 is restarted. FIG. 6 shows changes over time of the commanded valve opening (valve opening command value θd), actual valve opening (measured valve opening θm), motor torque, and PID enable signal. The motor torque is torque output by the motor 243 (see FIG. 3) that drives the air valve 240 . In FIG. 6, as in FIG. 5, the measured valve opening θm, the PID enable signal, and the motor torque show the behavior when the present embodiment is applied with a solid line. When the control is stopped) is shown by a dotted line.

Even at the time of restarting shown in FIG. 6, the occurrence of problems can be prevented by performing the same process as to whether or not PID control can be performed as in steps S3 to S5 of the flowchart of FIG.

When the fuel cell is stopped at time T4, the valve opening command value θd linearly and monotonously decreases to bring the air valve 240 into the fully closed state. The valve opening measurement value .theta.m starts decreasing to follow the command value .theta.d with a time delay with respect to the change in the valve opening command value .theta.d.

When the restart is started at time T5, conventionally, the PID enable signal is unconditionally switched off at the time of restart, and the PID control is disabled. Therefore, when the air valve 240 is moving in the closing direction and the valve actual opening degree θm is still considerably open to the fully closed state, when the PID control is stopped, the motor torque column in FIG. As indicated by the dotted line in , the motor torque is 0 and the torque on the brake side is no longer generated. Transition to the closed state. As a result, the valve body 242 hits the valve main body 241 side at a rapid speed, and the valve body 242 of the air valve 240 bounces back, as indicated by the dotted line in the item of the measured value θm in FIG. 6 .

On the other hand, in this embodiment, this problem can be avoided by performing the determination in step S3 of the flowchart of FIG. That is, since the valve opening measured value θm does not satisfy the second condition that the measured value θm is less than the measured value threshold value θt2, the processing of steps S3→S5 in the flowchart of FIG. PID control is continuously implemented. As a result, after the restart, as indicated by the solid line in the column of motor torque in FIG. 6, torque on the brake side is generated. It can transition up to the valve opening command value θ1. As a result, it is possible to prevent the valve body 242 of the air valve 240 from colliding with the valve main body 241 side, and to suppress wear of the parts of the air valve 240 .

After the valve opening measured value θm becomes less than the measured value threshold θt2 at time T6, the second condition that the valve opening measured value θm is less than the measured value threshold θt2 is satisfied. →The process of S4 is executed, the PID enable signal is switched off, and PID control is no longer performed.

As described with reference to FIGS. 4 to 6, according to the fuel cell system 10 of the present embodiment, when both the first condition and the second condition are satisfied, the air valve (discharge flow control valve 240) is By adopting a configuration in which PID control of the valve opening degree is not performed, it is possible to suppress overshoot in the opening direction of the valve body 242 at the time of system startup, and at the time of system restart, the valve body 242 moves toward the valve body 241 at high speed. can be prevented from colliding with each other, it is possible to stably control the valve opening degree of the discharge flow control valve 240 .

The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples by those skilled in the art are also included in the scope of the present disclosure as long as they have the features of the present disclosure. Each element included in each specific example described above and its arrangement, conditions, shape, etc. are not limited to those illustrated and can be changed as appropriate. As long as there is no technical contradiction, the combination of the elements included in the specific examples described above can be changed as appropriate.

In the above embodiment, the exhaust flow rate adjustment valve 240 was described as an example of a valve that determines whether PID control (feedback control) can be performed. Other valves can be applied as long as they are arranged in the flow path (air supply system 200, hydrogen gas supply system 300) through which the reactant gas supplied to 100 flows.

In the above embodiment, the configuration in which the discharge flow rate adjustment valve 240, which is the control target of PID control, is a butterfly valve as shown in FIG. 3 was exemplified.

10 fuel cell system 61 valve opening determination unit 62 air valve control unit 63 air valve opening sensor (valve opening measurement unit)
240 discharge flow control valve (valve)

Claims (1)

a valve arranged in a flow path through which reactant gas supplied to the fuel cell flows;
a valve opening determination unit that determines the opening of the valve based on the flow rate of the reaction gas calculated from the target power generation amount of the fuel cell;
a valve opening measuring unit for measuring the opening of the valve;
a valve control unit that feedback-controls the operation of the valve based on the valve opening command value determined by the valve opening determining unit;
with
The valve control unit is
The valve opening command value determined by the valve opening determining unit satisfies a first condition that the valve opening command value is less than the command value threshold, and the valve opening measured value measured by the valve opening measuring unit is less than the measured value threshold. when the second condition is satisfied, the feedback control of the valve is not performed;
performing the feedback control of the valve when the first condition or the second condition is not satisfied;
fuel cell system.

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